Haitian infants born in Miami have evidence on an acquired immunodeficiency disease syndrome (AIDS) and develop multiple severe infections associated with marked reversal of T-cell subsets, immune complexes and elevated IgG levels. A case study is proposed to define the natural history of this disease and to develop prognostic parameters, as well as provide a basis for benefit-risk analysis of various forms of intervention such as drugs or isolation. At the present rate of case detection 10-20 new cases will be enlisted each year. The frequency and duration of virus excretion and host responses to selected members of the Herpesvirus family will be monitored longitudinally to assess how AIDS patients differ from comparison groups in their primary responses to common viruses. Evidence suggests that a novel agent causes AIDS. Pediatric patients may provide an optimal source for detection of etiologic agents. Tissues of AIDS patients will be studied for evidence of integrated viral DNA sequences related to human retroviruses and for sequences related to transforming genes that may be activated in tissues. Family members of index cases and comparison families will be followed to detect evidence of immunologic abnormalities. Individuals with immunologic abnormalities such as T-cell subset reversal will then be followed prospectively to determine if clinical disease is an inevitable consequence of T-cell subset reversal or if subclinical abnormalities occur. A field study to determine risk factors associated with the development of immunodeficiency will be done by home visitation and questionnaires. Family members of index cases and comparison families will be followed prospectively to determine the frequency of acquired immunodeficiency in family units. As means of obtaining pilot data on transmission of immunodeficiency, pregnant AIDS women, pregnant consorts of adult Haitian males with AIDS and pregnant mothers of index infants and all their newborn infants will be studied for immune function and for virus excretion.